The High Pass was first created before the First Age by Oromë the Vala, in order to allow for a crossing of the mountains by the Eldar. Later in the First Age the High Pass was used by the Dwarves, who connected their roads (the Great East Road and the Men-i-Naugrim through Mirkwood) with it.

It's worth noting that there are actually two passes at this location. The lower pass is more prone to being blocked by Orcs, hence most travellers using the higher pass outside of those rare occasions when the Orcs were suppressed.